Continuous arch wire closing loop design, optimization, and verification. Part II.

A systematic approach to closing loop design for use in continuous arch wires was presented in Part I. The design process used Castigliano's theorem to derive equations for moment-to-force ratio (M/F) in terms of loop geometry. The equations were used to optimize designs by optimizing M/F to produce tooth movement via translation. Further refinements were performed by use of finite element simulations of designs. In Part II the predicted results are verified experimentally. The result of this process is a new design, the Opus loop, which is capable of delivering a nonvarying target M/F within the range of 8.0-9.1 mm inherently, without adding residual moments by twist or bends (commonly gable bends) anywhere in the arch wire or loop before insertion. The resulting precise force systems delivered with nonvarying M/F can move groups of teeth more accurately to achieve predetermined anteroposterior treatment goals for esthetics and/or stability. The experimental results show that the loops must be bent accurately to achieve their design potential. The negative impact on M/F of various dimensional changes to the loop design are presented. Experimental data is presented illustrating the improved performance of the new design over standard available designs. Suggested applications of the design for varying anchorage requirements are presented, along with a case report in which rigorous protraction requirements were met.